<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../react18/react.development.js"></script>
  <script src="../react18/react-dom.development.js"></script>
  <script src="../react18/babel.min.js"></script>
</head>

<body>
  <button id="btn">修改vDOM,并重新渲染</button>
  <div id="app"></div>
  <script type="text/babel">
    /* 
      diff算法的比较
        Diff算法比较只会在同层级进行, 不会跨层级比较,如果当前层级不一致则直接替换
        diff算法在某个层级比较一致的话,会进入层级内部再次比较,默认按照DOM书写顺序进行比较

        伪代码:
        旧的虚拟DOM
          <li>html</li>
          <li>css</li>
          <li>js</li>

        新的虚拟DOM
          <li>react</li>
          <li>html</li>
          <li>css</li>
          <li>js</li>
    */
    /* const arr = ["html","css","js","jq"]
    const vDOM = (
      <ul>
        {
          arr.map(item => (<li>{item}</li>))
        }  
      </ul>
    )
    const root = ReactDOM.createRoot(document.getElementById('app'));
    root.render(vDOM)


    //给按钮绑定点击事件,修改数据 然后重新得到新的vDOM 重新渲染
    const oBtn = document.getElementById('btn');
    let i = 0;
    oBtn.onclick  = function(){
      arr.unshift("react" + i++);
      const vDOM = (
        <ul>
          {
            arr.map(item => (<li>{item}</li>))
          }  
        </ul>
      )
      root.render(vDOM)
    } */



    const arr = ["html","css","js","jq"]
    const VDOM = (
      <div>
        <ul>
          {arr.map(item => <li>{item}</li>)}
        </ul>
      </div>
    )
    const root = ReactDOM.createRoot(document.getElementById('app'))
    root.render(VDOM)

    const oBtn = document.getElementById('btn');
    let i = 1
    oBtn.onclick = function(){
      arr.unshift("react"+ i++)
      const VDOM = (
        <div>
          <ul>
            {arr.map(item => <li>{item}</li>)}
          </ul>
        </div>
      )
      root.render(VDOM)
    }


  </script>
</body>

</html>